With the Ethernet developing towards the direction of multi-service carrying, especially, a plurality of services with higher and higher requirements for reliability and real time of the network, ring networking is widely deployed in Ethernet to enhance reliability of the network. In the network protection methods for ring networks, rapid (less than 50 ms) protection switching is usually required. Currently, rapid protection switching technology includes RFC3619 of Internet Engineering Task Force (IETF), and G.8032 of the International Telecommunication Union (ITU-T), etc.
Take Ethernet ring protection technology as an example, and FIG. 1 shows a structure diagram of the Ethernet ring in the related art. As shown in FIG. 1, node A˜node F are nodes that have Ethernet switching functions; network NI connects to node B; network N connects to node D. Network M and network N communicate via two physical paths, i.e., network N←→node D←→node C←→node B←→network M, or network N←→node D←→node F←→node F←→node A←→node B←→network M.
Ethernet ring protection technology defines a ring protection link and a control node, that is, in a case of an Ethernet ring without a failure, the link on the ring blocking the data message for preventing the ring being formed is called as the ring protection link, and the switching between the active link and the protection link on the ring network is achieved by operating the ring protection link. The node with the ring protection link is called as a control node (or a master node).
FIG. 2a is a schematic diagram of forwarding the data stream by an Ethernet ring shove in FIG. 1 without a failure. As shown in FIG. 2a, the ring network comprises nodes A, B, C, E, and F, and links <A,B>, <B,C>, <C,D>, <D,E>, <E,F>, <F,A>. Suppose node A is the control node, and the direct link <F,A> connecting to port a2 is the ring protection link.
When there is not a failure on links of the ring, the control node blocks the data message-forwarding function of the port a2 that connects to the ring protection link, and thus a loop is not formed in the network, which prevents broadcast storms caused by the network loops. As shown in FIG. 2a, the control node A blocks the protection data message-forwarding function of the port a2. The communication path between network M and network N is: network M←→node B←→node C←→node D←→network N.
When a failure occurs on the link, the control node A opens the data message-forwarding function on the port a2 that connects to the ring protection link, thereby ensuring service connectivity. FIG. 2b is the schematic diagram of data stream protection switching under a case of the Ethernet ring with a failure. As shown in FIG. 2b, suppose the link <B,C> on the ring has a failure, the control node A opens (enables) the data message-forwarding function on the port a2, and then the new communication path between network M and network N is: network M←→node B←→node A←→node F←→node E←→node D←→network N.
ITU-T G.8032 version 1 (G.8032v1) has been released in June, 2008. In this version, the standard supports two types of protocol messages: the SF protocol message and the NR protocol message. The two types of protocol messages are respectively described as follows.
The SF protocol message is the Signal Fail (SF) message, and its functions are: when a node detects a failure, the node periodically sends the SF protocol message along the ports on the ring to notify other nodes on the ring that a failure occurs on the ring network. After receiving the SF message, the nodes on the ring that have blocking ports (the ports without a failure that block data messages) enable the data message-forwarding function of the blocking ports.
The NR protocol message is the No Request message, and its functions mainly have the following two aspects:
when detecting that the failure on the adjacent link recovers, the node periodically sends the NR message along the two ports on the ring to notify other nodes on the ring that the link failure recovers.
After receiving NR messages sent by other nodes, the control node starts a Waiting Timer (WTR timer). When the WTR timer times out, the control node blocks the data-forwarding function of the ports, and periodically sends the NR (RB) message (RB: RPL Link Blocked) along the two ports on the ring to notify other nodes on the ring that the ring protection link has been blocked.
After releasing ITU-T G.8032v1, ITU-T SG15 group started to draft G.8032 version 2 (G.8032v2). In the standard of G.8032v2, two types of protocol messages are increased based on G.8032v1: Force Switch (FS) and Manual Switch (MS) protocol messages. These two types of protocol messages are both the method for artificially making the blocking ports on a ring. That is, when node on a ring starts FS (or MS), the node periodically sends the FS (or MS) message along the two ports on the ring to notify other nodes on the ring that a force switch (or a manual switch) occurs. After receiving the FS (or MS) message, the nodes on the ring that have blocking ports (the ports without a failure that block data messages) enable the data message-forwarding function of the blocking ports. The difference between FS and MS is that the priority of FS is higher than that of SF and the priority of MS is lower than that of SF, which means when the ring network has a failure, FS protocol messages can exist in the ring network, while MS protocol messages will be refused by the nodes in the ring network.
A 4-bit Request/State field is adopted to identify the type of a protocol message in the protocol message of ITU-T G.8032v1. The code values of SF and NR in this field are shown in Table 1.
TABLE 1FieldProtocol message code valueMessage descriptionRequest/State0000NR1011SFOthersReserved
A 4-bit Request/State field is adopted to identify the type of a protocol message in the protocol message of ITU-T G.8032v2. The code values of SF, NR, MS and FS in this field are shown in Table 2.
TABLE 2MessageFieldProtocol message code valuedescriptionRequest/State0000NR1011SF0111MS1101FS1110EventOthersReserved
When Request/State field=1110 (Event), new types of protocol messages may be defined combined with Sub-code field, as shown in Table 3.
TABLE 3Sub-codeRequest/State (code)(code)Message description11100000FlushOthersReserved
The Flush message in Table 3 is mainly used for address refresh outside sub-ring domain in multi-ring scenarios. The details refer to the ITU-T G.8032v2 standard. Here the description about will be not repeated.
Currently, protocol messages of G.8032v1 and G.8032v2 are distinguished by the Version field. The value of the Version field in G.8032v1 protocol messages is 0x00, and that in G.8032v2 protocol messages is 0x01.
At present, the method for implementing forward compatibility of G.8032v2 (compatible with G.8032v1) includes:
1) when a node only supports the G.8032v1 version, the node filters out the FS and MS protocol packets, and only forwards ES and MS protocol messages without further processing;
2) when a node supports the G.8032v2 version, the node can recognize FS and MS protocol messages, and processes the FS and MS protocol messages accordingly.
However, in the present compatibility solutions, problems may exist under a plurality of cases. FIG. 3a and FIG. 3b respectively are the first schematic diagram and the second schematic diagram showing the compatibility problems existing in the existing ring networks. Details are as follows.
As shown in FIG. 3a, suppose that nodes A, B, C and F support ITU-T G.8032v1 and nodes D and E support ITU-T G.8032v2; and node A is the control node. When no failure occurs in the ring network, node A blocks the data message-forwarding function of port a2 and periodically sends NR (RB) messages along the two ports on the ring at the same time.
When force switch is started at port e2 of node E in the system, node E periodically sends FS protocol messages along port e1 and port e2 outwards. Since nodes A, B, C and F support ITU-T G.8032v1, they filter out the received FS protocol messages and do not perform further processing, and therefore, node A does not enable the data message-forwarding function of port a2 after receiving the FS messages, and two blocking ports always exist on the ring, which dramatically decreases the network performance.
Similarly, in FIG. 3b, since the control node A supports ITU-T G.8032v1, it only filters out the MS protocol messages sent by node F and does not perform further processing. Therefore, node A does not enable the data message-forwarding function of port a2 after receiving the MS messages, and two blocking ports always exist on the ring, which dramatically decreases the network performance.
In conclusion, the existing forward compatibility solutions of ITU-T G.8032v2 cause a case that multiple block points occurs in the ring network, which dramatically decreases the network performance.